This invention relates to the measurement of magnetic fields as in magnetic surveying, and particularly to the measurement of such fields with a degree of effectiveness not heretofore conveniently attainable.
It has long been known to perform magnetic surveying in order to determine the general configuration of the earth's magnetic field, as well as more localized features, such as bodies of ore and other subsurface entities influencing the magnetic field. Such surveying has been performed by various techniques. One of these involves the use of so-called flux gate magnetometers. Flux gates are electrically driven saturable-core inductors whose electrical output varies as a function of magnetic field strength parallel to the core. In flux gate magnetometers, quadrature oriented flux gates are used to define a plane perpendicular to the magnetic field to be measured. This is done by using the output from these quadrature flux gates to position them so as to null their outputs. An additional flux gate, perpendicular to the plane so defined, then actually measures the intensity of the field. To make these measurements rapidly over large areas of terrain, the whole installation is normally carried in an airplane, mounted in a boom which protrudes from the plane so as to locate the sensing equipment as far as possible from the magnetic fields associated with the plane itself.
This prior art technique is inherently ineffective to measure one important parameter of the magnetic field, namely changes in its angle of orientation.
The measuring flux gate itself is maintained parallel to the field being measured, and therefore is incapable of providing any angle-representative output. The outputs of the quadrature flux gates defining the plane perpendicular to the field are nulled, and therefore also provide no output useful for angle measurement.
Various expedients have been proposed, which do have the possibility of measuring angular changes. However, these other techniques are also vastly more complex and costly.